The present invention relates to a transparent heating instrument, for use in a microscope, for heating a to-be-examined object which is placed thereon and a culture dish and a transparent heating instrument for examining an object with naked eye.
Artificial insemination is conventionally put in practice for breeding of a stock. It also has been put in practice for the human race for the purpose of treating infertility. For such artificial insemination, it is necessary to examine the vitality and appearance of the sperm to be introduced with a microscope and confirm the faultlessness of the sperm beforehand. Since sperm generally has the optimum activity at 37.degree. C. to 38.degree. C. though it varies according to the species of animals, it is preferable to perform the examination at this temperature.
For this purpose, the inventors of the present invention proposed a heating for microscopic examination described in International Publication No. WO87/3703. This heating device comprises a heater stage and a heating means. The heater stage has a transparent conductive film between top and bottom transparent glass plates.
In recent years, an inverted microscope has come into wide use. Since the lens system is disposed below the stage in the inverted microscope, it is preferable that a through hole is formed at the center part of the stage. By the through hole thus formed, checking of the magnification lens of the inverted microscope is made easier. Thus, it is preferable to form the through hole at substantially the central part of the transparent heating plate for the microscope, too.
The present inventors have found that it is unnecessary to form such a through hole if a thin transparent heating plate can be provided. But the thin transparent heating plate is not rigid.
Thus, it is a first object of the present invention to provide a transparent heating instrument, for use in a microscope, which allows a heating plate to be sufficiently thin; does not interrupt the rotation of a magnification lens when the transparent heating instrument is fixed to the stage of an inverted microscope even though it does not have a through hole at the center part thereof; and has a high strength.
As described above, in recent years, an inverted microscope has come into wide use. In the inverted microscope, the lens system is positioned below the stage. The transparent heating instrument installed on the stage has a cord for electrification. The cord extends downward from the lower surface of a frame-shaped housing of the transparent heating instrument. Thus, it occurs that the magnification lens gets caught by the cord while the magnification lens is being operated.
Thus, it is a second object of the present invention to provide a transparent heating instrument which prevents the magnification lens of the microscope from being caught by the cord thereof.
In the conventional transparent heating instrument, a conductive wire is fixed to an electrode of a transparent heating plate with conductive adhesive agent. Thus, the transparent heating plate cannot be heated to a temperature higher than the heat-resistant temperature of the conductive adhesive agent. That is, the conventional transparent heating instrument cannot be used at a high temperature.
Thus, it is a third object of the present invention to provide a transparent heating instrument which can be heated to a temperature higher than the heat-resistant temperature of the conductive adhesive agent.